REVERSION IN ORIENTATION TO LIGHT 509 



but three minutes later they were again negative. A minute trace 

 of acid was again added, the colonies became inactive and all 

 died in a few moments, 



2. On December 6 sodium hydrate was added step by step to a 

 solution containing numerous Spondylomorum colonies, until 

 enough had been added to make the solution n/62 NaOH on the 

 basis of pure water. It gave a faint alkaline test with litmus- 

 paper. In the beginning of the experiment some of the colonies 

 were positive, others were negative. At the close all were neu- 

 tral, but no reversion in orientation had occurred. The following 

 day the colonies in the alkaline solution were in excellent condi- 

 tion, and five days later, December 12, they were still apparently 

 normal and strongly negative. At this time n/100 HCl was slowly 

 added step by step. The solution was tested with neutral red 

 from time to time and the orientation was noted. The results 

 obtained are presented in tabular form in table 1. 



The results obtained in these two experiments are essentially 

 hke those obtained in all of the numerous other similar tests 

 made. They show clearly that the addition of acids causes nega- 

 tive Spondylomorum to become positive, but they also seem to 

 show that the reversion in orientation produced by the addition 

 of acids is not due to the direct effect of the acids on the organisms, 

 for the colonies in most cases became positive before the alkalinity 

 of the culture solution was neutralized. Moreover, the results 

 obtained with pure distilled water support this contention. 



In distilled water of high^ purity Spondylomorum lives for 

 days and responds normally. In such solution the addition of a 

 very small amount of acid proves fatal. For example, in one 

 experiment, specimens put into n/ 15,000 HCl lived only a few 

 moments. In n/6666 HCl they lived for some time, and in 

 n/20,000 HCl they were still alive and apparently normal after 

 two days. Whether or not addition of acid to pure distilled water 

 causes reversion in orientation was not definitely ascertained, 



1 The water used in these experiments was very generously supplied by the 

 late Prof. H. C. Jones. It was redistilled from two Jena glass flasks in series, one 

 containing chromic acid, the other barium hydrate, and condensed in a block-tin 

 condenser. 



